1. Field of the Invention
The present invention relates to a conveyor chain driven by a sprocket to transport an object along a conveyance path.
2. Description of the Related Art
There are known various conveyor chains used for conveyance of an object along a conveyance path. A typical example of such known conveyor chains is shown here in FIGS. 13A and 13B, which is composed of a series of chain units connected with one another by connecting pins in an endless fashion. Each of the chain units includes a rectangular top plate A1 for carrying thereon an object to be conveyed, front and rear bushing portions A2 and A3 located at a leading edge and a trailing edge, respectively, of the top plate A1 on the back side of the top plate A1. Adjacent two chain units are connected by a single connecting pin extending through the rear bushing portion A3 of one chain unit and the front bushing portion A2 of the other chain unit.
The bushing portions A2, A3 disposed on the back side of the top plates A2 are adapted to engage a sprocket (not shown) to move the conveyor chain in a conveyance direction.
In the conventional top plate type conveyor chain described above, since the bushing portions A2, A3 disposed on the back side of each top plate A1 collide with the bottom of a sprocket tooth when the chain comes into mesh with the sprocket, a large impact sound is generated. The impact sound occurs repeatedly with a frequency generally equal to the frequency of meshing between the chain and the sprocket. This periodic impact sound forms a main part of the noises generated during conveyance travel of the chain. Another problem is that the collision occurring periodically between the bushing portions of chain and the tooth bottoms of sprocket can cause a movement of the free span of the chain in a direction perpendicular to the chain travel but in the same plane as the chain and the sprocket. This vibratory movement of the chain can also produce a vibratory noise which increases the noise level during conveyance travel of the chain.
The conventional top plate type conveyor chain does not have any means effective to prevent the chain from moving or oscillating in the width direction of the chain while the chain travels along a conveyance path. Accordingly, when the lateral oscillatory movement of chain occurs, an object carried on the top plates A1 becomes unstable in position and may sometime fall from the top plates A1.
With the foregoing difficulties associated with the prior art in view, an object of the present invention is to provide a conveyor chain which is capable of reducing the impact sound or the contact sound during meshing with a sprocket to thereby suppress the noise and vibration during conveyance, is able to carry a conveyed object stably during conveyance without causing lateral movement which may result in accidental falling of the object, and can be assembled with a relatively small number of parts used.
To achieve the above object, according to the present invention, there is provided a conveyor chain comprising a number of chain units connected with one another by connecting pins in an endless fashion. The chain has an outer peripheral side adapted to carry an object for conveyance of the object along a conveyance path and an inner peripheral side adapted to engage a sprocket for transmitting power from the sprocket to the chain. Each of the chain units is composed of a plurality of inverted tooth plates disposed in the width direction of the chain. Each of the inverted tooth plates has a pair of inverted teeth formed on one side thereof for meshing with teeth of the sprocket, and a pair of pin-accommodation holes formed therein for receiving a pair of connecting pins, respectively, of the connecting pins. Each of the connecting pins connecting adjacent two chain units in such a manner that the inverted tooth plates of one chain unit are interleaved with the inverted tooth plates of the other chain unit.
When the conveyor chain of the foregoing construction comes into mesh the sprocket, the engagement surfaces of inverted tooth plates (formed by the inside flanks and/or the outside flanks of the inverted teeth) slide on sprocket tooth flanks while maintaining a small incident angle with respect to the sprocket tooth flanks. This sliding contact can reduce the impact energy or force produced between the inverted tooth plates and the sprocket. It is, therefore, possible to eliminate the large impact sound that occurs in the meshing between of conventional top plate type conveyor chain and a sprocket. In addition, since the periodic sound resulting from the impact sound at the onset of meshing can be eliminated, and since the vibratory noise resulting from collision at the bottom of the sprocket tooth or the contact sound resulting from contact with the tip of the sprocket tooth does not occur, the noise level of the conveyor chain during its travel when operating as a conveyor is greatly reduced.
In one preferred form of the present invention, the teeth of inverted tooth plates located at one end of each chain unit and the teeth of inverted tooth plates located at the other end of the same chain unit are aligned with each other in the longitudinal direction of the chain. As an alternative, the teeth of inverted tooth plates located at one end of each chain unit and the teeth of inverted tooth plates located at the other end of the same chain unit are offset half a pitch in the width direction of the chain.
In another preferred form of the present invention, two inverted teeth of each chain unit that are located at opposite outer ends in the width direction of the chain are adapted for slide contact with opposite end faces of the sprocket and have a height larger than the height of the other inverted teeth of the same chain unit. As an alternative, a central inverted tooth of each chain unit that is located at the center in the width direction of the chain is adapted for slide contact with opposed inside surfaces of two laterally juxtaposed sprockets and has a height larger than the height of the other inverted teeth of the same chain unit.
In a further preferred form of the present invention, the chain units each have a flat guide surface disposed on the inner peripheral side of the chain and extending in the longitudinal direction of the chain for slide contact with a guide rail disposed along the conveyance path. The flat guide surface may be formed by a truncated tip end face of at least one selected tooth of the inverted teeth.
In a still further preferred form of the present invention, two inverted teeth of each chain unit that are located at opposite outer ends in the width direction of the chain each have a guide lug projecting in a lateral outward direction for slide contact with a side guide rail provided on each side of the chain along the conveyance path, so as to prevent the chain from floating during travel.
It is preferable that each of the pair of inverted teeth has a slit opening to a tip end and opposite end faces of the inverted tooth. By thus providing the slit, the teeth are elastically deformable when meshing with the sprocket teeth. This elastic deformation is effective to reduce the slide sound to a negligible level during meshing engagement between the teeth of the inverted tooth plates and the sprocket teeth.
In another preferred form of the present invention, each of the chain units further has a slat disposed on the respective other sides of the inverted tooth plates and extending across the width of the chain transversely across the inverted tooth plates. The slat may be integral with the inverted tooth plates of each chain unit, or assembled with the inverted tooth plates of each chain unit.
It is preferable that the slat of each chain unit has a wing portion projecting in a lateral outward direction from an outermost inverted tooth plate of the chain unit, the wing portion having a straight leading edge and a convexly arcuate trailing edge when viewed from the direction of conveyance, and the pin-accommodation holes that are located adjacent to the trailing end of the chain unit comprise an oblong hole having a major axis extending substantially parallel to the longitudinal direction of the chain. This arrangement enables the conveyor chain to pass a curved portion in a horizontal plane in the conveyance path without causing collision or overlapping of the adjacent slats.